scrapy中有一個引數：DOWNLOAD_DELAY 或者 download_delay 可以設定下載延時，不過Spider類被初始化的時候就固定了，爬蟲執行過程中沒發改變。

隨機延時，可以降低被封ip的風險

程式碼示例

random_delay_middleware.py

# -*- coding:utf-8 -*-

import logging
import random
import time


class RandomDelayMiddleware(object):
    def __init__(self, delay):
        self.delay = delay

    @classmethod
 

    def from_crawler(cls, crawler):
        delay = crawler.spider.settings.get("RANDOM_DELAY", 10)
        if not isinstance(delay, int):
            raise ValueError("RANDOM_DELAY need a int")
        return cls(delay)

    def process_request(self, request, spider):
        delay = random.randint(0
 
, self.delay)
        logging.debug("### random delay: %s s ###" % delay)
        time.sleep(delay)

使用方式：

custom_settings = {
        "RANDOM_DELAY": 3,
        "DOWNLOADER_MIDDLEWARES": {
            "middlewares.random_delay_middleware.RandomDelayMiddleware": 999,
        }
    }

說明：
RANDOM_DELAY

total_delay = DOWNLOAD_DELAY + RANDOM_DELAY

更精確的說，應該是：

DOWNLOAD_DELAY + 0 < total_delay < DOWNLOAD_DELAY + RANDOM_DELAY